China’s purchase of Nidera makes it a large player in grain exports from Argentina   China’s move to buy a controlling stake in Netherlands-based agricultural trading company Nidera has divided the waters among farmers in Argentina, one of the world’s leading soy exporters, with larger producers celebrating the purchase and smaller ones raising concerns about potential market concentration. State-run China Grains and Oils Group Corporation (COFCO) announced on February 28 that it had bought a 51…